For the rich, taxes are all disposable income. For the 99%, taxes are cutting into their living wage. The rich might not be able to afford a 3rd house; the rest of us struggle to pay a mortgate/rent on the 1st one.
Taxes remove money from the economy and also create the demand for the fiat currency.
A government that didn't spend any money while collecting taxes would create massive deflation and markets wouldn't clear. On the other hand, a government that didn't collect any taxes and simply spent the money would create inflation.
If for the increase in money supply there is a corresponding increase in GDP, there is no real inflation since the money is chasing more goods and services.
Guess what - that means more poor people getting what they need, before rich people get to fund golden toilets or something. And yes, I will think this way even when I am a billionaire.
A liquid wealth tax. The actually wealthy have many vehicles for hedging against inflation, from owning durable property, to complex financial instruments.
It's more complicated than that. As a first approximation inflation is a transfer of wealth from from savers to debtors. However, there are many under-appreciated details based on tax implications of such things as paying real taxes on illusory income. (nominal gains which result in an real-after-tax loss) I learned a lot about this from this guy: http://danielamerman.com/
It depends on how that wealth is stored. Most wealthy people invest in things that are resilient or that even perform better under inflation. It's really the middle class that gets hit and the poor the worst because minimum wage doesn't go up that fast but prices definitely do.
Where did you get the idea that disposable income increases for everyone? How could that be even possible?